The use of tetraalkylammonium and hexaalkylguanidinium salts as phase transfer catalysts in the preparation of various polymers is known. In particular, U.S. Pat. No. 5,132,423 discloses the reaction of bisphenol salts with halo- or nitro-substituted phthalimides in an organic medium to produce bisimides which, upon conversion to dianhydrides and reaction with diamines, form polyetherimides. U.S. Pat. No. 5,229,482 discloses a similar phase transfer catalyst reaction of bisphenol salts with halo- or nitro-substituted bis(phthalimido) derivatives of aromatic diamines or with similar compounds, resulting in the direct formation of polyetherimides and other polyether polymers. The phase transfer catalysts employed according to U.S. Pat. No. 5,132,423 and 5,229,482 are guanidinium salts and especially hexaalkylguanidinium salts.
There are four general methods for the synthesis of an organoalkoxysilane compound:
1. Hydrosilylation of allyl- or vinyl-functional compound with trialkoxysilane. PA1 2. Hydrosilylation of allyl- or vinyl-functional compound with trichlorosilane and subsequent alcoholysis. PA1 3. Reaction of chioropropyltrimethoxysilane with a sodium or potassium salt of organic acid. PA1 4. Reaction of an aminoalkysisane with a carbonate to form the product via the carbamate. PA1 1,3,5-tris(trimethoxysilylpropyl) isocyan urate, PA1 1,3,5-tris(methyldimethoxysilylpropyl) isocyanurate, PA1 1,3,5-tris(dimethylethoxysilylbutyl) isocyanurate, PA1 1,3,5-tris(phenylmethylmethoxysilylpropyl) isocyanurate, and the like. PA1 --O(O)C--, PA1 --NH(O)C--, PA1 --NR.sup.1 (O))C--, PA1 .dbd.N(O)C--, PA1 --O(O)P.dbd., or PA1 --O(O)CO--
U.S. Pat. No. 3,517,001 discloses the first method and cites that isocyanurate-organosiianes have been prepared in the past by adding hydrosilanes to unsaturated isocyanates and more specifically allyl isocyanate in the presence of metal catalysts. This process is limited on a large scale because the hydrosilanes are expensive and the unsaturated isocyanates are typically highly toxic.
The first method suffers from many practical problems such as a slow hydrosilylation process, formation of byproducts containing internal olefins, use of toxic and low flash point reagents such as trimethoxy- or triethoxysilane.
The second method is described in U.S. Pat. No. 4,281,145. It teaches that bis(3-trimethylsilylpropyl) fumarate can be made by the hydrosilylation of diallyl maleate with trichlorosilane and subsequent methoxylation of the trichlorosilyl compound to the desired product. Unfortunately, the handling of trichlorosilane is very dangerous due to the low boiling point, very high reactivity and toxicity of this material. Also the methanolysis process is difficult to control and produces large amounts of waste.
The third method is described in U.S. Pat. Nos. 3,607,901; 3,821,218, and 3,598,852. These methods are for synthesizing 1, 3, 5-tris (trialkoxysilylpropyl) isocyanurates. This process involves the reaction of potassium cyanate with chloropropyltnmethoxysilane in a polar aprotic solvent such as N,N dimethylformamide (DMF) which is toxic and difficult to remove. The reaction time is about 3 to 8 hours. The resulting material has purity about 70% and is highly colored.
Patents such as U.S. Pat. No. 5,218,133 and U.S. Pat. No. 4,880,927 disclose the fourth method and disclose that aminoalkylsilanes can be reacted with carbonates such as dimethyl carbonate in basic conditions which will form the carbamate. The carbamate is then neutralized and converted to the isocyanurate by a lengthy, high temperature, subatmospheric pressure cracking reaction which necessitates the use of a cracking catalyst such as aluminum triethoxide and a base catalyst such as sodium acetate.
U.S. Pat. No. 4,946,977 discloses the preparation of methacryloxypropyltrimethoxysilane by contacting potassium methacrylate with chloropropyltrimethoxysilane in the presence of tetraalkylammonium halides as phase transfer catalyst. The yield of the reaction is below 90% and the resulting product usually has a dark color due the thermal decomposition of the catalyst.
European patent application 483,480 describes the preparation of methacryloxypropyltrimethoxysilane with high yield by the contacting of potassium methacrylate with chloropropyltrimethoxysilane in the presence of 4-N,N-dialkylaminopyridine as a catalyst. 4-Dialkyiaminopyridine is an effective catalyst in these processes but the use of dialkylaminopyridine is limited due to very high toxicity of these compounds.